This invention relates to a method for generating useful real-time feedback about tissue characteristics and the position of anatomical objects relative to at least one tool used during clinical procedures in living biological structures, employing an ultrasonic transducer/probe.
Thus, more specifically, the invention relates to the field of ultrasound imaging during a clinical procedure that involves a tool being inserted into the imaged scene, particular methods for combining the geometric localization of the said tools relative to the acquired ultrasound images.
The method to be described here comprises a combination of acquisition of ultrasonic images, localization of tools and/or tool trajectories used during the clinical procedure, processing of the ultrasonic images based on the knowledge of the position of the tools in the imaged scene in order to obtain visualizations with real-time feedback to the operator. The visualizations integrate information obtained both from the ultrasonic images and the geometric localizations of the tools in the imaged scene. The invention describes alternative procedures for obtaining the geometric localization of tools and describes how the said images and geometric localization's can be processed in order to obtain useful feedback based on the information content in both data sources (ultrasonic images and tool positions).
The method finds application in surgical, therapeutic and diagnostic procedures.
The term clinical procedure will be used throughout this invention to designate:
1. Any invasive diagnostic, therapeutic or surgical procedure as for example: open surgery, endoscopic/laparascopic surgery, cyst aspiration, biopsy (sampling), injection, implantation etc.
2. Any therapeutic and/or diagnostic procedure based on energy emission in terms of fields, waves or particles, for example: radiotherapy, laser therapy or ultrasound therapy (ultrasound hyperthermia or shockwaves)
3. Any similar clinical procedure where at least one mechanical object and/or energy field is applied to the imaged, living biological structures.
The term tool will be used throughout this invention to designate:
1. A surgical tool used in a clinical procedure, for example: a cutting or resecting device (scalpel, diathermy, scissors, suction, ultrasound aspirator, thermal knife, laser, argon beam), a coagulating device (monopolar or bipolar diathermy, laser), a stapler, biopsy forceps, needle, cannula etc.
2. An imaging device like an ultrasound catheter, ultrasound probe or any optical imaging system.
3. Combined devices such as an endoscope that includes imaging capabilities and at least one surgical tool as described above.
4. An external beam or energy field applied in for example: radiotherapy, laser therapy or ultrasound therapy.
5. Any similar devices or fields that can be coregistered with the acquired ultrasonic images.
The term quasi real-time will be used throughout this invention to designate that a process (like ultrasound data acquisition, position determination of tools in the imaged scene and/or data visualization) runs fast enough to allow for interactive feedback/operation by the user. This includes truely real-time where the absolute time delay between data acquisition and the final data visualization is below the acceptable level for interactive feedback. In addition, we will use the term quasi real-time to refer to processes that appear as truely real-time to the user.
This can for example be accomplished by a repetitive 3D ultrasound acquisition where the repitition rate exceeds the criteria for interactive operation, but where the position determination and data visualization are performed in real-time based on the latest available 3D data set.
The term positioning system will be used throughout this invention to designate:
1. Any system that provide information about the position and/or direction of an ultrasound probe, a tool or other objects within the operating theater. The positioning system can optionally provide mechanical support by limiting the movement of the ultrasound probe, tool or other objects to a predetermined space, plane, direction or point.
2. The positions and/or directions are determined by measurements or by predetermined geometry.
3. Position measurement is achieved by any magnetic, electromagnetic, optical or acoustical system (wireless or not) or by any mechanical arrangement with angle and/or position sensors.
Technology development has accelerated the use of non-invasive and minimally invasive techniques in medicine. The use of energy fields, waves, needles, catheters and endoscopic instruments allow diagnosis, treatment and surgical procedures in most parts of the human body. The patient trauma is reduced, the cost and the hospitality time is reduced, and procedures can be performed that was not possible before.
Such techniques require positioning and manipulation of tools in relation to organs and other biological structures within the body, all which may be hidden for visual inspection of the human eye. The irregular and unpredictable shape and position of most biological structures and organs makes absolute positioning within the body difficult or impossible from the outside. Positions and shapes may also change during the procedure. Various imaging techniques are currently in use to provide geometric information to the operator, prior to, during and after the procedure.
Preoperative MR, CT or X-ray scans are commonly used in order to utilize a description of a lesion and its relation to other structures. Allthough MR and CT systems provide 3D data, these techniques suffer from some drawbacks: i) The instruments are huge, non-portable and the investments costs are high. ii) Interactive imaging and surgery is normally not possible. iii) Biological structures that move or deformate during the clinical procedure or between diagnostic imaging and the clinical procedure, limits the value of such imaging techniques. iv) CT and X-ray systems expose the patient to ionizing radiation which may damage tissue and cause cancer.
Endoscopic techniques based on optics or a video camera provide high quality and real-time visualizations which allows intra-operative procedures. However, the lack of penetration through biological structures limit their use.
The ultrasound technology has several advantages in that it penetrates through biological structures, the instruments are portable, and interactive imaging during the procedure is possible, even in real time. This means that structures that change during the clinical procedure can be monitored continously or repetitively. There are large potentials in integrating the use of ultrasound imaging and Doppler techniques in clinical procedures for the purpose of monitoring and guidance.